Video: Refining the matte

Now this is a lot more along the lines of the typical green screen job that you will be faced with. And I've already gone ahead and keyed this out for you, but I just want to show you some of things that contribute to a bad green screen. So, in case you have some kind of say in the production workflow, you can tell the production crew what to look out for so that could get a better key. Oftentimes, when people are a working on a film set, they are pros with lights they are pros with cameras, but they are not really sure of what we need in postproduction to get the best results. And so being able to know some of these tips to be able to pass those down the line so that when you get this footage it looks better.

In After Effects CS5 Essential Training, author Chad Perkins discusses the basic tools, effects, and need-to-know techniques in Adobe After Effects CS5, the professional standard for motion graphics, compositing, and visual effects for video. The course provides an overview of the entire workflow, from import to export, as well as detailed coverage of each stage, including animating text and artwork, adding effects to compositions, working in 3D, and rendering and compressing footage. Exercise files are included with the course.

Refining the matte

Now this is a lot more along the lines of the typical green screen job thatyou will be faced with.And I've already gone ahead and keyed this out for you, but I just want to showyou some of things that contribute to a bad green screen.So, in case you have some kind of say in the production workflow, you can tell theproduction crew what to look out for so that could get a better key.Oftentimes, when people are a working on a film set, they are pros with lightsthey are pros with cameras, but they are not really sure of what we need inpostproduction to get the best results.And so being able to know some of these tips to be able to pass those down theline so that when you get this footage it looks better.

Well it really pays to know some of things.So, I am going to apply Keylight to this and again I am going to click theEyedropper and click the green.Now you'll notice they we're having some issues here. We have some light greenhere and some darker green here and typically for the best green screen as wesaw in the last movie you want a uniform green. That's the ideal.In this case, we really don't have that so I'm just going to pick a green that Ithink is kind of representative of the whole, like an average.And you could see instantly, as opposed to the last movie when we had a reallygreat key right after, that this looks obviously very terrible.

So, what I am going to do is change this to Status and when we change it toStatus that way we can see the little squares here.These little squares are because of the compression artifacts.We are not getting an even key because of the way this was compressed.You could tell as I go into the Screen Matte area and I adjust Clip Blackas before is that we're having a lot of uneven edges because, again, of this compression.Now I am just going to go ahead a turn this layer off and turned that Complete layer on.The Complete layer is me just so basically getting somewhat of a good key out aKeylight as best as I could, but we're still seeing a lot of jagged edges and Ihave some like wispy hair.

This is never going to be a perfect key because the footage is terrible.That's one thing that you can understand and pass on your clients is that you can dosome great things, but you're not a miracle worker.You can't take terrible awful footage and make it perfect.Thankfully, in After Effects CS5, there is a new effect called Refine Matte andif we apply this here to this footage,we'll get some help with this bad key. It's not going to make things perfect, butit definitely saves you a lot of time in trying to solve problems.The first thing that it does automatically with this Smooth value, a defaultvalues of two here, is it smoothes the key out.

So, if we zoom in extra-- and it's going to look a little pixilated becausewe zoomed it so close.But here is before with the Keylight key and here is after with Refine Matte.So, it's smoothed things out considerably even though it is a little bit toosmooth. I might want to take this down to maybe 1.3 or so, which is putting a littlebit of a corners back in these edges here.We could also feather our matte. We could also choke meaning restrict the matte.If we increase this too much, we could see that like it starts eroding away atthe edge around here.

But it's a subtle fine-tuned adjustment so you don't have to worry aboutcompletely destroying the edge of the matte, and it also goes intonegative value to expand the edge if you want that too, but just be aware that it's here.Generally choking is though of kind of like a cheat.So, don't eat away at the edge of your matte unless you really need to.In this case, we might need to. I'll leave this set to a value of eight for the time being.Chatter, we talked about all of these settings when we talked about Roto Brush earlier on.But I am going to increase Chatter to hundred percent so that way from frame toframe I have less jitter on the edges of my key.

And one of the cool things about the Refine Matte Effects is that it also looks at motion blurwhen there is motion blur, and it decontaminates the edges from motion blur.At one point, I move my hand around pretty quickly here and you could see thatthere is a motion blur.And typically, this is really hard to get a clean key when there is motion blurbecause you get green from the background in the motion blur and yet RefineMatte somehow manages to decontaminate those edges for the motion blur.There is some junk going on here, what we could use go here to the IncreaseDecontamination value.

Actually it's called Increased Decontamination Radius and what we can do isincrease this very slightly.This parameter is very sensitive, so increase it too much and it starts lookinglike that, which is not good.So, just a little bit. It helps get some of that junk out of thefingers, but all in all, I mean this is the before, and this is the after.We lost a little bit of hair, so you may have to go fiddle with this alittle bit more, but all the same, we got the decontamination out of themotion blur. And again, this is what it looks like before and this is whatit looks like after Refine Matte.

Find answers to the most frequently asked questions about After Effects CS5 Essential Training .

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Q: In the "Creating a fireball" movie in Chapter 6, the author showed how to make a fireball. Unfortunately, it all centered around a blob layer that he made without showing how to make a blob layer. How does one go about creating a blob layer like the one used in the video?

A: To create a blob layer, make a shape layer using the Pen tool. Animate the anchor points over time to make it move. These concepts are reviewed in depth in Chapter 4, "Learning to Animate."

Q: In the Chapter 5 video "Understanding precomposing," the exercise file provided does not seem to match up with the file the instructor uses. My file does not include a "Biker Body" layer. Is there an error in the exercise file?

A: Unfortunately, the exercise file originally distributed for this chapter was incorrect. A new file was issued in February 2011. If you downloaded the exercise files prior to then, you can download the corrected file on the Exercise Files tab of the course page.

Q: How do I transition from one piece of animated type to another in After Effects?

A: There isn't an effect that can create these types of transitions. It's really a matter of animating the type and camera, using basic keyframing and positioning.

If
you understand the basics of moving the anchor point of a type layer,
animating the parameters of that layer (Scale, Rotation, Position,
etc.) and then separately animating the camera around the type layers, you
can achieve different types of transitions. Check out the following videos for more information:

Learn by watching, listening, and doing, Exercise files are the same files the author uses in the course, so you can download them and follow along Premium memberships include access to all exercise files in the library.

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Learn by watching, listening, and doing! Exercise files are the same files the author uses in the course, so you can download them and follow along. Exercise files are available with all Premium memberships.
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